/**
 * 图片压缩
 * @param {图片对象} img
 * @param {预留参数} Orientation
 * 使用方法
 *  // 进行压缩
 *   let image = new Image();
 *   image.src = // 图片base64
 *   image.onload = () => {let imgData = this.hdImageCompress(image)}
 */
const hdImageCompress = (img, Orientation) => {
  let canvas = document.createElement('canvas')
  let ctx = canvas.getContext('2d')
  // 瓦片canvas
  let tCanvas = document.createElement('canvas')
  let tctx = tCanvas.getContext('2d')
  let initSize = img.src.length
  let width = img.width
  let height = img.height

  // 如果图片大于四百万像素，计算压缩比并将大小压至400万以下
  let ratio
  if ((ratio = width * height / 4000000) > 1) {
    console.log('大于400万像素')
    ratio = Math.sqrt(ratio)
    width /= ratio
    height /= ratio
  } else {
    ratio = 1
  }
  canvas.width = width
  canvas.height = height
  // 铺底色
  ctx.fillStyle = '#fff'
  ctx.fillRect(0, 0, canvas.width, canvas.height)
  // 如果图片像素大于100万则使用瓦片绘制
  let count
  if ((count = width * height / 1000000) > 1) {
    count = ~~(Math.sqrt(count) + 1) // 计算要分成多少块瓦片
    // 计算每块瓦片的宽和高
    let nw = ~~(width / count)
    let nh = ~~(height / count)
    tCanvas.width = nw
    tCanvas.height = nh
    for (let i = 0; i < count; i++) {
      for (let j = 0; j < count; j++) {
        tctx.drawImage(img, i * nw * ratio, j * nh * ratio, nw * ratio, nh * ratio, 0, 0, nw, nh)
        ctx.drawImage(tCanvas, i * nw, j * nh, nw, nh)
      }
    }
  } else {
    ctx.drawImage(img, 0, 0, width, height)
  }
  // 修复ios上传图片的时候 被旋转的问题
  // if (Orientation !== '' && Orientation !== 1) {
  //   switch (Orientation) {
  //     case 6: // 需要顺时针（向左）90度旋转
  //       this.rotateImg(img, 'left', canvas)
  //       break
  //     case 8: // 需要逆时针（向右）90度旋转
  //       this.rotateImg(img, 'right', canvas)
  //       break
  //     case 3: // 需要180度旋转
  //       this.rotateImg(img, 'right', canvas) // 转两次
  //       this.rotateImg(img, 'right', canvas)
  //       break
  //   }
  // }
  // 进行最小压缩
  let ndata = canvas.toDataURL('image/jpeg', 0.3)
  console.log('压缩前：' + initSize)
  console.log('压缩后：' + ndata.length)
  console.log('压缩率：' + ~~(100 * (initSize - ndata.length) / initSize) + '%')
  tCanvas.width = tCanvas.height = canvas.width = canvas.height = 0

  return ndata
}

export default hdImageCompress
